DRAGGING BRAKES (OVER TIME) LX

My brakes drag (I'm assuming), and the dragging worsens after about 10-15 minutes. The car also pulls to the left, especially when applying pressure to the brakes.

When I first start my car and begin to drive, the drag is extremely subtle, almost unnoticable.
But after driving about 10 or 15 minutes, the dragging worsens to an almost undrivable situation.

Things I have noticed are, in cool weather, or when driving at night, the brake pedal sinks down much further before grabbing, and the dragging is less intense and takes longer to intensify.
But if the weather is warm, or my car has been exposed to sunlight, the brake pedal barely goes down before it grabs, and the brakes will usually begin dragging within 2 minutes.

We've replaced the brake hoses, replaced the left caliper, and replaced the brake pads. The hoses have been bled numerous times.
Another thing, when the hoses were bled, we noticed the brake fluid is extremely thick, almost like syrup. The fluid we use is DOT 3.

A friend suggested cleaning the master cylinder.
A mechanic suggested (since he had no clue what was wrong) replacing everything. I'm thinking it's something simple, just nobody seems to know what it is.

Any ideas? If your suggestion ends up fixing the problem, expect a donation. : D

Hey Shi,
Need to start with a little detective work. Make sure the rear parking brake cables are not frozen. Also make sure the rear shoes are adjusted properly and the self adjusters work properly.

Drive the vehicle until you fell the brakes are dragging. Touch each wheel and let us know if you find some that are hotter than the others.

If you find a hottie check the steel line for any kinks or crushing. Jack the wheel up onto jackstands and spin it by hand. If the wheel is dragging start by cracking open its brake line at the master cylinder to see if it frees up. If not continue down to the next junction and do it again. Go all the way to the caliper/wheel cylinder bleeder until it releases the pressure.

Have you replaced all 4 brake hoses? A sound bit of wisdom is to always replace calipers or wheel cylnders in pairs to maintain equal performance.

By any chance has anything other than brake fluid been added to the mastercylinder?